State Data

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Overview

Potential statistical 'outliers' were determined separately for each state. Specifically, outliers are defined here as soil lead results that are two and three standard deviations greater than the average. Spatial outliers were defined using Anselin's Local Moran's I statistic to identify observations that were statistically significantly different from other nearby observations.1 The spatial outliers include observations that are surrounded by observations with significantly lower concentrations. The definition of spatial outlier used here also includes local clusters of two or more observations with significantly higher concentrations than surrounding observations.

It is important to note that labeling an observation as an 'outlier' does not imply there is something necessarily 'wrong' with the observation; e.g., outliers should not automatically be omitted from an analysis or discarded as invalid. The method for handling outliers varies depending on the objectives of the analysis. Furthermore, there are many ways to define outliers; the definition that is used should support the objective of the analysis. The objective of this web site is to simply describe the data. The effect of the outliers on summary statistics of the data is illustrated by comparing the statistics in the tables provided below. The user is encouraged to download the data for further exploration and analysis, including a determination of which observations should be considered outliers, given the objectives of their analysis.